This invention relates to systems and methods for processing and collecting blood, blood constituents, or other suspensions of cellular material.
Today people routinely separate whole blood, usually by centrifugation, into its various therapeutic components, such as red blood cells, platelets, and plasma.
Conventional blood processing methods use durable centrifuge equipment in association with single use, sterile processing systems, typically made of plastic. The operator loads the disposable systems upon the centrifuge before processing and removes them afterwards.
Conventional blood centrifuges are of a size that does not permit easy transport between collection sites. Furthermore, loading and unloading operations can sometimes be time consuming and tedious.
In addition, a need exists for further improved systems and methods for collecting blood components in a way that lends itself to use in high volume, on line blood collection environments, where higher yields of critically needed cellular blood components, like plasma, red blood cells, and platelets, can be realized in reasonable short processing times.
The operational and performance demands upon such fluid processing systems become more complex and sophisticated, even as the demand for smaller and more portable systems intensifies. The need therefore exists for automated blood processing controllers that can gather and generate more detailed information and control signals to aid the operator in maximizing processing and separation efficiencies.
The invention provides systems and methods for processing blood and blood constituents that lend themselves to portable, flexible processing platforms equipped with straightforward and accurate control functions.
More particularly, the invention provides systems and related methods for sensing the presence of targeted cellular blood species during extracorporeal blood separation or processing. The systems and methods tailor the sensing parameters to the particular objectives of the blood processing procedure selected to be accomplished. Different cellular blood species are targeted for detection for different selected blood processing procedures. The systems and methods differentiate among different cellular blood species for detection, according to the blood processing procedure selected.
According to one aspect of the invention, blood processing systems and methods provide a blood separation chamber constructed and arranged for rotation about an axis separate blood into a plasma layer and an adjoining region comprising different first and second cellular blood species arranged in layers according to density. The systems and methods employ a collection line, which includes a pump to remove the plasma layer from the blood separation chamber. The pump operates to control flow through the collection line in response to pump control signals. The systems and methods also include a sensor assembly in the collection line to detect concentration of first and second cellular blood species in the collection line.
According to this aspect of the invention, a controller coupled to the sensor assembly and the input operates to generate the pump control signals. The generation of the pump control signals varies according to the type of blood collection procedure selected to be conducted. When a first blood collection protocol is selected, the controller generates a pump control signal when the sensor assembly detects changes in concentration of the first cellular blood species in the collection line. When a second collection protocol is selected, the controller generates a pump control signal when the sensor assembly detects changes in concentration of the second cellular blood species in the collection line.
In one embodiment, the first cellular blood species comprises platelets, which reside in the adjoining region immediately adjacent the plasma layer. The second cellular blood species comprises red blood cells, reside in the adjoining region, separated by platelets and leukocytes from the plasma layer. In this arrangement, the sensor assembly is able to differentiate between platelets and red blood cells to carry out, in association with the controller, the objectives of the particular blood processing procedure selected.
For example, when plasma is targeted for collection, the controller generates a pump control signal when the sensor assembly detects platelets. The pump control signals control the pump to minimize the presence of platelets in the collected plasma stream. Leukocytes and red blood cells, which are arranged in subsequent layers in the adjoining layers according to density, are thereby also excluded from the plasma stream. This makes possible the collection of plasma, if desired, free or essentially free of contamination by unwanted cellular species, like platelets or leukocytes or red blood cells.
As another example, when red blood cells are targeted for collection, the controller generates a pump control signal when the sensor assembly detects red blood cells. The pump control signals control the pump to minimize the presence of leukocytes and platelets in the collected red blood cell stream. This makes possible the collection of red blood cells, if desired, free or essentially free of contamination by unwanted cellular species, like platelets or leukocytes.
As another example, the buffy coat can be targeted for collection. The buffy coat comprises a platelet-rich layer and a subsequent red blood cell-rich layer separated from the plasma layer by the buffy coat. When a buffy coat collection protocol is selected, the sensor assembly to detect changes in concentration of platelets, which denotes the plasma-platelet interface at the leading edge of the buffy coat. The sensor assembly also detects changes in concentration of red blood cells, which denotes the red blood cell-buffy coat interface at the trailing edge of the buffy coat. The pump control signal or signals control the pump to collect essentially only the buffy coat, free or essentially free of dilution by plasma and free or essentially free of red blood cells.
In one embodiment, the controller includes an input for selecting different blood processing protocols.
In one embodiment, the sensor assembly optically detects changes in concentration of the first and second cellular blood species.
Other features and advantages of the inventions are set forth in the following specification and attached drawings.
According to another aspect of the invention, systems and methods are provided for optically differentiating between the presence of platelets and red blood cells in a plasma flow. The systems and methods provide a first emitter of light at a first wavelength (xcex1) having a known optical attenuation for platelets at the first wavelength (xcex5plateletsxcex1) and a known optical attenuation for hemoglobin at the first wavelength (xcex5Hbxcex1). The systems and methods also provide a second emitter of light at a second wavelength (xcex2) having a known optical attenuation for platelets at the second wavelength (xcex5plateletsxcex2) and a known optical attenuation for hemoglobin at the second wavelength (xcex5Hbxcex2). According to this aspect of the invention:
xcex1xe2x89xa0xcex2;
xcex5plateletsxcex1≈xcex5plateletsxcex2
xcex5Hbxcex1 greater than xcex5Hbxcex2,
The systems and methods provide a path transparent to light at the first and second wavelengths to convey the plasma flow past the first and second emitters. The systems and methods provide a light detector to receive light emitted by the first and second emitters through the path and to generate signals proportional to intensities of received light. The systems and methods analyze the signals to derive intensities of the received light at the first and second wavelengths and generate an output representing presence of a blood cell concentration in the plasma flow. The systems and methods compare changes in intensities of received light the signals over time to derive changes in intensities of received light at the first and second wavelengths over time. The systems and methods generate an output that differentiates between changes in intensity attributable to changes in platelet concentration in the plasma flow and changes in intensity attributable to changes in red blood cell concentration in the plasma flow.
According to another aspect of the invention, systems and methods are provided for optically sensing characteristics of a blood flow free in a way that is not sensitive to ambient lighting conditions or electromagnetic energy interference. The systems and methods provide a light source having a driver circuit that includes a source of constant current and a modulator that modulates the constant current at a selected carrier frequency for transmission to the light source. The systems and methods provide a light sensor for receiving light from the light source and producing a modulated output proportional to received light intensity. The systems and methods provide a receiver circuit including a bandpass filter coupled to the light sensor to receive the modulated output and having a center frequency at or near the selected carrier frequency to eliminate frequency components above and below the selected carrier frequency.
In one embodiment, the selected carrier frequency is below the frequency components comprising electromagnetic interference.
In one embodiment, the selected carrier frequency is above the frequency components comprising ambient light.